1. Field of the Invention
The present invention relates to a liquid-discharging recording head (inkjet recording head) that performs recording by discharging liquid such as ink (hereinafter simply referred to as ink), and a liquid-discharging recording apparatus (inkjet recording apparatus) including the head.
2. Description of the Related Art
In recent inkjet recording apparatuses, a detachably loaded inkjet recording head has readable information (individual information) inherent thereto, such as an ID (identity) code and driving characteristics for an ink discharging mechanism. For example, this allows the inkjet recording apparatuses to acquire information about the loaded inkjet recording head, and to execute driving control best suited for ink discharging from the head. For that purpose, a ROM (read only memory) mounted on an inkjet recording substrate is known. Japanese Patent Laid-Open No. 3-126560 (corresponding to U.S. Pat. No. 6,231,155) discloses that an EEPROM (electrically erasable programmable ROM) is mounted.
It is also known that a base substrate of an inkjet recording substrate in an inkjet recording head is provided with a resistor indicating information inherent in the recording head, together with a layer that forms an ink discharging mechanism. In this case, the inkjet recording apparatus can acquire information about the loaded inkjet recording head by reading the value of the resistor provided on the base substrate. This method is effective when the amount of information is relatively small.
Japanese Patent No. 3438683 discloses that, when a layer that forms an ink discharging mechanism is formed on a base substrate of an inkjet recording substrate, fuses serving as ROMs are simultaneously formed. The fuses are selectively blown out by using, for example, a logic circuit, thereby writing and storing binary data.
When a detachable inkjet recording head is loaded in the recording apparatus, it is inevitably touched with the hand of the user. In this case, there is a risk that electric terminals of the head for connection to the recording apparatus will be affected by static electricity. In an inkjet recording head disclosed in Japanese Patent Laid-Open No. 7-060953 (corresponding to U.S. Pat. No. 6,074,041), a discharging circuit is provided around contact pads that establish electrical connection to the main unit of an inkjet recording apparatus in order to protect the head from such static electricity.
However, in the inkjet recording head in which an information storage element, such as a ROM or an EEPROM, is mounted, as disclosed in Japanese Patent Laid-Open No. 3-126560, the configuration of the apparatus is inevitably complicated. Therefore, there are demands to increase productivity and to reduce the size and weight of the head. Basically, a ROM chip is useful when the volume of recording data is high. However, when the volume of recording data is not high, the ROM chip is sometimes disadvantageous in cost, and there is a need to improve this disadvantage.
In contrast, in the method in which elements for storing information inherent in the head are formed in the layer forming process, it is possible to prevent the configuration of the head from being complicated and to prevent the number of processes from increasing in order to store the inherent information. For this reason, a small and light head having individual information can be provided with a simple configuration and at low cost without reducing productivity.
In this inkjet recording head that can store individual information, it is particularly important to give consideration to static electricity. That is, fine information storage elements provided on the inkjet recording substrate to store information inherent in the head are not resistant, particularly, to static electricity. Therefore, the information storage elements may be broken or information stored in the information storage element may be rewritten by static electricity.
In the inkjet recording head disclosed in Japanese Patent Laid-Open No. 7-060953, an adverse influence of static electricity can be avoided, but it is necessary to form a special discharging circuit on the substrate. For this reason, various improvements are expected to enhance the space efficiency and to reduce the size and cost of the head.